The present invention relates to a device as defined in the preamble of claim 1. The invention also relates to use of the device according to claim 14 or 15.
In mass treatment, e.g. in conjunction with the so-called rubbish traps of sand separators, knot scrubbers and screens, various valve solutions have been used. The solution used e.g. in conjunction with centrifugal cleaners comprises a container placed at the lower end of the centrifugal cleaner and provided with a first valve in its upper part and a second valve in its lower part. The rubbish trap system functions as follows. When the upper valve is opened, any impurities heavier than the mass being processed descend into the container, which is closed by the lower valve. When the container has been filled to a sufficient level, the upper valve is closed, and after it has been closed up, the lower valve is opened, whereupon the material in the container descends into the space located after the lower valve, e.g. into a piping system. After this, the lower valve is closed and air is removed from the space between the valves. The upper valve can now be opened and the above-described cycle of operation repeated. The rubbish trap system is usually controlled by using a control means such as a logic system or computer, e.g. a process computer. Prior-art rubbish trap systems have the drawback that both valves may be left open due to a malfunction, in which case the mass can flow through the rubbish trap system at full process pressure.
There are also blocking feeders which have a rotor rotating about its axis and divided by partitions into adjacent compartments which are filled and evacuated one after the other. The disadvantages of prior-art blocking feeders include a complex structure and e.g. sealing problems due to uneven wear. One of the drawbacks of prior-art solutions is that they may admit gases into the process, for instance air when an empty blocking feeder is returning to the filling position.
The object of the present invention is to achieve a solution in which material can be removed from a higher pressure into a lower pressure without the drawbacks of prior art. Another object of the invention is to achieve a completely new type of solution for implementing a so-called rubbish trap for various cleaner devices, screens, sorters and equivalent.
The invention is characterised by what is presented in the claims.
The apparatus of the invention has numerous significant advantages. The apparatus comprises a passage for a so-called by-pass flow to prevent gases potentially harmful to the process from getting into the process from the lower pressure. By-pass flow promotes the emptying of the chamber space of a feed element e.g. by forcing the rubbish towards the discharge port. The device provides a very high degree of reliability in operation. It can be easily connected to control systems. Periodic operation in opposite directions results in uniform wear of the sealing elements. Moreover, in rubbish trap use, the device is reliable and permits no flow through it in the event of malfunction As compared with known rubbish trap systems, the apparatus makes it possible to replace an aggregate of several devices with a single device. The sealing elements of the device are replaceable. In addition, the solution allows the apparatus to be used in widely different conditions, among other things in consequence of the materials used in the sealing elements.